Antibody-based computing

An application of the antibody’s flexible recognition (i.e. multi-reactivity) to antigenic epitopes to a combinatorial computing is just getting started. The present study discusses an antibody-based computation algorithm to solve a combinatorial problem: the stable marriage problem. The stable marriage problem supposes n men and n women, and each person ranks all members of the opposite sex in a strict order of preference. Under given preference lists, to detect all of “stable” n couples including no affair pairs means to solve this problem. Our algorithm replaces a man and a woman with an antigenic epitope and an antibody respectively, and re-scales a man (woman)’s preference to a woman (man) as strength of a binding affinity between an epitope to the man and an antibody to the woman. Under these settings, we demonstrate a parallel progression of immune reactions can solve the stable marriage problem. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

An adaptive algorithm based on the immune system and its application to adaptive noise neutralization

We propose an adaptive algorithm based on some features of the immune system (a selection-based mechanism compatible with Edelman’s selectionist principle, self/nonself reference, and negative/positive selection). The algorithm proceeds in three steps: diversity generation, establishment of self-tolerance, and memorizing nonself. This algorithm may typically be used to model the system of distributed agents where the system (the self) as well as the environment (the nonself) are unknown or cannot be modeled. An agent-based architecture based on the local memory hypothesis and a network-based architecture based on the network hypothesis are discussed. The agent-based architecture is elaborated with applications to an adaptive system where knowledge about the environment is not available. An adaptive noise neutralizer is formalized and simulated for a simple plant. Some part of this work has been presented at ICEC 1996, IROS 1996, and AROB 1999.     

A network visualization of stable matching in the stable marriage problem

The stable marriage problem (SMP) seeks matchings between n women and n men which would result in stability, and not lead to divorce or extramarital affairs. We have introduced a network consisting of nodes which represent matchings, and links between nodes which attain stability by exchanging a partner between two pairs. The network is depicted with nodes laid out to involve several coordinates which indicate either women’s satisfaction or men’s or both. With the network visualization, regularity and symmetry can be made conspicuous in specific instances of the SMP such as the Latin SMP.     

Emergence of observable rules in a spatial game system

This study focuses on player’s strategies observed from outside our original spatial game iterated by players, each of which is placed in a lattice site on a two-dimensional square lattice. A particularity of the game lies in the fact that a player’s strategy is not given, but is constructed dynamically in response to the spatial pattern of the player’s actions. This means that the strategy can evolve in time. However, the simulations revealed unexpected results. It was found that all the strategies observed from outside did not evolve, but were fixed in time. This article enumerates all the observed strategies in detail, and examines their characteristics.     

Spatial strategies in a generalized spatial prisoner’s dilemma

Many strategies, such as tit-for-tat, have been proposed in the iterated prisoner’s dilemma (IPD) in which the prisoner’s dilemma (PD) is carried out repeatedly with two players. A spatial version of the iterated prisoner’s dilemma (SPD) has been studied, where a player at each site plays the IPD game with all the players in the neighborhood. However, the strategies studied in the SPD consider the past actions of a single opponent only. We studied spatial strategies that depend on the configuration of actions taken by all neighbors (as opposed to conventional temporal strategies). Since generosity can be considered as a spatial strategy, we first investigate the generosity required when an action error is involved. We also propose several spatial strategies that outperform many others.This work was presented, in part, at the 9th International Symposium on Artificial Life and Robotics, Oita, Japan, January 28–30, 2004     

Suppression of Dynamic On-Resistance Increase and Gate Charge Measurements in High-Voltage GaN-HEMTs With Optimized Field-Plate Structure

The dynamic on-resistance increase associated with the current collapse phenomena in high-voltage GaN high-electron-mobility transistors (HEMTs) has been suppressed by employing an optimized field-plate (FP) structure. The fabricated GaN-HEMTs of 600 V/4.7 A and 940 V/4.4 A for power-electronics applications employ a dual-FP structure consisting of a short-gate FP underneath a long-source FP. The measured on-resistance shows minimal increase during high-voltage switching due to increased electric-field uniformity between the gate and drain as a result of using the dual FP. The gate-drain charge Q _gd for the fabricated devices has also been measured to provide a basis for discussion of the ability of high-speed switching operation. Although Q _gd /A (A: active device area) was almost the same as that of the conventional Si-power MOSFETs, R _on A was dramatically reduced to about a seventh of the reported 600-V Si-MOSFET value. Therefore, R _on Q _gd for 600-V device was reduced to 0.32 OmeganC, which was approximately a sixth of that for the Si-power MOSFETs. The high-voltage GaN-HEMTs have significant advantages over silicon-power MOSFETs in terms of both the reduced on-resistance and the high-speed switching capability.     

Alkene selectivity enhancement in the oxidation of propane on calcium-based catalysts

The oxidation of propane has been investigated in the presence and absence of tetrachloromethane (TCM) on calcium hydroxyapatite (CaHAp), Ca₃(PO₄)₂, CaSO₄ and CaO at 723 K. In the absence of TCM, the conversion of C₃H₈ on CaHAp was 7.7–9.2% during 6 h on-stream while that on Ca₃(PO₄)₂, CaSO₄ and CaO was 0.6, 0 and 0.2–0.4%, respectively. The principal products on all catalysts in the absence of TCM were CO and CO₂ with small selectivities to C₃H₆ and C₂H₄ (both 5–6%) observed on CaHAp. Upon addition of TCM, the selectivity to C₃H₆ on all catalysts and the conversion of C₃H₈ on CaSO₄ increased while, with increasing time-on-stream, the changes in the conversion and selectivity were dependent upon the nature of the catalysts. XPS and XRD analyses provide evidence for the presence of chlorine in the surface and/or bulk of three of the catalysts, suggesting that chlorinated species on the solids play a role in the selectivity enhancement, but the absence of chlorine from the sulphate demonstrates the dissimilarities of the catalysts in their abilities to sorb and decompose TCM. This revised version was published online in July 2006 with corrections to the Cover Date.     

Friction property study of the surface of ZDDP and MoDTC antiwear additive films using AFM/LFM and force curve methods

The friction properties and material differences of the surface of ZDDP and MoDTC antiwear additive films, which give clear evidence of different friction coefficients in a pin-on-disc test, have been studied using atomic force microscopy (AFM)/lateral force microscopy (LFM) and force curve methods. The AFM/LFM observations show that the friction force on the surface of MoDTC additive films over the sliding area of a steel disc is lower and the friction force of ZDDP additive films is higher than that of afilmless area. Lateral force scope-trace evaluations reveal that the ratio of the friction forces on the surface of the ZDDP film, the filmless area, and the MoDTC film under the same normal force is approximately 1.5:1.0:0.7. Force curve measurements indicate that the surface materials of the ZDDP film, thefilmless area, and the MoDTC film differ according to their attractive forces, that is 29 nN for the ZDDP film, 22 nN for the filmless area, and 12 nN for the MoDTC film. These results correspond to the friction behaviour in the pin-on-disc test and also agree with the idea of the formation of solid MoS₂ lubricant from MoDTC additives on the surface of the antiwear film.     

Effects of poly(propylene carbonate) additive prepared from carbon dioxide on the tensile properties of polypropylene

We investigated the effect of a rubbery poly(propylene carbonate) (PPC) additive on the tensile properties of isotactic polypropylene (iPP). PPC materials were produced from carbon dioxide gas. Although the elongation of iPP was reduced at higher elongation speeds, PPC addition improved the elongation at break at higher elongation speeds. iPP/PPC blends showed a high drawability while maintaining a high stress level. The failure mechanisms at high elongation speeds were different between the iPP and iPP/PPC samples. Craze‐like voids appeared along the stretching direction for pure iPP, whereas the PPC additive yielded craze‐like voids that were perpendicular to the stretching direction. The addition of PPC doped with carbon nanodots enhanced the yield toughness of iPP at high elongation speeds. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45266.     

Compatibility of binary blends of polypropylene with ethylene-α-olefin copolymer

The compatibility for binary blends of isotactic polypropylene with rubbery ethylene-α-olefin copolymers having various α-olefin contents was investigated by means of differential scanning calorimetry, X-ray analysis, transmission electron microscopy, and dynamic mechanical analysis. It was found that “α-olefin rich” in ethylene-1-butene copolymers and in ethylene-1-hexene copolymers were miscible with amorphous polypropylene chains, when the α-olefin content is above 50 mol %. On the other hand, the blends with “ethylene rich” (above 50 mol % of the ethylene content) in ethylene-1-butene copolymers and ethylene-1-hexene copolymers showed a microheterogeneous morphology. © 1996 John Wiley & Sons, Inc.